Since A. Geim and K. Novoselov have simply and successfully isolated a graphene monolayer, which is composed of flat plates having a thickness corresponding to one sp2-bound carbon atom, from graphite using a so-called Scotch tape method in 2004, a variety of research groups have conducted ardent research on graphene in an attempt to understand and employ abnormal characteristics such as superior electronic characteristics (semimetals, zero-gap semiconductors, a high electron mobility of 15,000 cm2V−1s−1, and a resistance of 10−6Ω lower than silver), thermal conductivity (5,000 Wm−1K−1), optical characteristics (transparency and absorbing only 2.3% of white light), a high mechanical strength (200 times higher than steel), and a high surface area per unit mass (solution characteristics, and a face area of 3,000 m2g−1).
Owing to such unique characteristics, graphene has been, for example, known to be highly useful in being used in transparent conductive films, electrodes for energy storage devices, filed-effect devices, microelectronic devices, chemical and biological sensors, and filler-conductive polymer composites.
Most of conventional research has focused on two-dimensional (2D) structures. However, the shape of graphene having a three-dimensional (3-D) structure has been more recommended to make use of most of the excellent physical and electronic characteristics, a high surface, and chemical functions.
In recent years, Chen el al processed a 3-D graphene foam using a template-directed chemical vapor deposition (CVD). The optimized conductivity of the 3-D graphene foam is 10 S·cm−1, which is an order of calculation of approximately 6 higher than that of a chemically derived graphene-base composite.
Also, the conductivity of graphene is maintained even after pores are filled with polydimethylsilonxane (PDMS). However, CVD treatment requires a high processing temperature and an etching process, which makes it necessary to make a graphene foam on a nickel or copper foam. And, an additional process of transferring a graphene film onto another substrate is essentially required. However, such a process has a problem in that it is expensive and a large amount of time is required.
Further, conventional CVD methods have a problem in that a metal should be etched again with an acid after a nickel foam is processed, and exposed to a high temperature of 1,000° C. to perform chemical vapor deposition.